Head and neck cancer

Published on 09/04/2015 by admin

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8 Head and neck cancer

AA. Edwards, RL. Mendes,

Introduction

Head and neck oncology is challenging. It demands a thorough knowledge of head and neck anatomy to guide multi-modality treatment and the treatment itself can lead to significant impairment in important functions such as swallowing, facial expression and speech. Tumours arising within various head and neck subsites can differ in presentation, clinical course and therapeutic options.

Cancers of the head and neck account for around 6% of malignancies worldwide. It is more common among men, with a male-female ratio of 2–3 : 1. Squamous head and neck cancers tend to affect patients between the ages of 40–70 years. The incidence varies geographically – for instance, nasopharyngeal carcinoma is most frequent in the Far East.

Aetiology

The important aetiological factors in squamous cell carcinomas of the head and neck include:

• Tobacco – smoking or chewing tobacco is the strongest risk factor for squamous cell carcinomas (SCC) of the head and neck, with more than 90% of patients having a history of tobacco use.
• Alcohol – increased alcohol consumption is associated with an increased risk of head and neck SCC, and has been shown to have a synergistic effect with tobacco in the development of SCCs.
• Viral infections:

• Human papilloma virus – About a quarter of head and neck SCC specimens contain HPV and about 90% of these are positive for HPV-16. HPV-16 is particularly associated with oropharyngeal SCC.
• Epstein–Barr virus has been implicated in nasopharyngeal carcinoma. Plasma levels of EBV DNA before treatment and after radiotherapy have been correlated with outcome and survival.

• Other risk factors:

• Lower socioeconomic status is associated with SCC of the oral cavity and larynx.
• Chewing betel quid – a mixture of tobacco, slaked lime and areca nut, wrapped in betel pepper leaf – is popular in India and parts of South East Asia. It is associated the development of oral submucous fibrosis and leucoplakia and is a risk factor for developing carcinoma of the oral cavity.
• Occupational risk factors include: asbestos (larynx), wood dusts (nasal cavity, nasal sinuses, nasopharynx and larynx), nickel (maxillary sinus) and pesticides (larynx).
• UV exposure is a risk factor for SCC of the lip.
• Previous head and neck irradiation increases the risk of subsequent head and neck malignancies.

Pathogenesis and pathology

SCC is thought to develop in a stepwise progression from squamous metaplasia to dysplasia, through carcinoma-in-situ to invasive squamous cell carcinoma. These histological changes are accompanied by molecular alterations which disrupt the regulation of cell proliferation, by inactivating tumour suppressor genes and activating oncogenes.

The majority (90%) of malignant tumours of the head and neck are squamous cell carcinomas. The WHO classification of head and neck cancers is outlined in Box 8.1.

Box 8.1
WHO Classification of malignant head and neck tumours

• Squamous cell carcinoma and variants such as verrucous carcinoma
• Nasopharyngeal carcinoma
• Salivary gland tumours – acinic cell carcinoma, mucoepidermoid carcinoma, adenoid cystic carcinoma
• Adenocarcinoma
• Lymphoma
• Small cell carcinoma
• Carcinoid
• Sarcoma
• Metastasis

Anatomy

Figure 8.1 shows the anatomical sites in the head and neck. Figure 8.2 demonstrates the anatomical levels of neck nodes and the typical regional lymphatic drainage for head and neck subsites, which are important in planning surgery and radiotherapy. In the unoperated neck, the pattern of lymph node drainage is relatively predictable for different tumour subsites. The risk of occult lymph node metastasis varies according to the primary site and the size of the primary tumour. Clinical assessment of this risk of cervical nodal metastasis dictates subsequent decisions on inclusion of lymph node groups within a neck dissection or radiotherapy target volume during the definitive treatment.

image

Figure 8.1 Anatomy of the head and neck region.

image

Figure 8.2 Anatomical levels of neck nodes.

Presentation

Most patients with head and neck cancer present with local symptoms due to the growth and depend on the site of tumour (see later).

Evaluation of patients with head and neck cancer

Important features in the history for head and neck cancer patients are:

• Duration and intensity of symptoms and signs
• Age
• Socioeconomic status
• Tobacco and alcohol use
• Co-morbid conditions: smoking-related illness, respiratory disease, cardiac disease, diabetes, liver disease, peripheral vascular disease, immunodeficiency, poor nutrition
• History of previous malignancy or pre-malignancy (especially in the head and neck region). In patients with recurrent disease or second malignancy, details of previous surgery and/or radiotherapy should be sought to guide further treatment

Clinical examination

The whole oral cavity and teeth should be inspected carefully (after removing any dentures). The tongue, cheeks, and floor of mouth should be palpated bi-manually. The ears and nose should be examined for mass lesions, discharge or bleeding. The pharynx and larynx should be examined using flexible fibreoptic nasoendoscopy or indirect laryngoscopy and the mobility of the vocal cords assessed. The neck should be palpated for enlarged lymph nodes or thyroid masses. In patients presenting with metastatic carcinoma in a cervical lymph node, an occult primary should be sought, with particular attention paid to the base of tongue, tonsil, nasopharynx and piriform fossae.

Investigations and staging

The objectives of the clinical assessment of a patient with a suspected head and neck cancer are:

• to establish a histological diagnosis
• to stage the disease
• to exclude synchronous tumours of the upper aerodigestive tract
• determine fitness for radical treatments.

Tissue diagnosis

• Fine needle aspiration/core biopsy may be used to sample enlarged lymph nodes.
• Examination under anaesthesia (EUA) with panendoscopy is often used to obtain biopsies to establish a histological diagnosis, and to clinically stage the tumour.

Imaging

• Suspicious cervical nodes may be further characterized by ultrasound examination of the neck.
• CT and/or MRI of the head and neck region are used to assess the extent of the primary tumour and the regional lymph nodes (Figure 8.3). MRI is superior for assessing soft tissue infiltration, cartilage invasion and perineural spread. CT is useful for assessing bone involvement and has the advantage of being better tolerated by patients with swallowing difficulties because of its faster speed of acquisition. USS of the neck also has a role in neck staging.
• CT chest (or chest X-ray) may be needed to rule out pulmonary metastases in locally advanced disease. Chest X-ray, however, may not detect small volume metastatic disease.
• 18FDG PET-CT has a role in assessing suspected tumour recurrence and in detecting occult primary tumours.
image

Figure 8.3 MRI of nasopharyngeal cancer.

Staging

TNM staging is based on the primary tumour size and/or extent, regional lymph node metastasis and distant metastatic spread (Box 8.2).

Box 8.2
A general TNM staging of head and neck tumour

Stage I T1N0M0 tumour of ≤2 cm
Stage II T2N0M0 tumour of >2–4 cm
Stage III T3N0M0 tumour of >4 cm
  T1–3N1M0 ipsilateral single node ≤3 cm
Stage IV T4N0–1M0 involving adjacent structures
  Any T N2M0 ipsilateral single node >3–6 cm (N2a)
    ipsilateral multiple nodes <6 cm (N2b)
    contralateral or bilateral nodes <6 cm (N2c)
  Any T N3M0 nodes >6 cm
  Any T, any N, M1 Distant metastasis

T4 tumours are divided into T4a (resectable) and T4b (unresectable). Hence stage IV can be IVa (T4a), IVb (T4b) or IVc (M1).

Larynx and pharynx has T staging based on local spread, whereas nasopharynx has separate T and N staging.

Management of head and neck cancers

Pre-treatment assessment

Management of head and neck cancers is complex, and needs a multidisciplinary approach. All patients require assessment of performance status, dentition, swallowing and nutrition. Dental assessment is important in minimizing late side effects of radical radiotherapy such as dental caries and osteoradionecrosis. Maintaining adequate nutrition is a challenge in patients with head and neck cancer. Patients who are malnourished or at risk of becoming malnourished need dietetic assessment and often intervention is needed. All patients with locally advanced head and neck cancer need a swallowing and language therapy (SALT) assessment prior to radical treatment. Patients are encouraged to stop smoking and minimize alcohol intake during radiotherapy.

Principles of treatment

Early stage disease (stages I–II/T1–2N0M0)

Early stage disease is usually managed with either surgery or radiotherapy. The choice of treatment is based on location of tumour and anticipated morbidity. Radiotherapy results in a local control rate of 85–95% for T1 and 70–85% for T2 lesions. Treatment of the neck should be considered in addition to the treatment to the primary site. Node negative head and neck cancers with a >15–20% risk of occult cervical node metastasis (all cancers except <2 cm lesions in oral cavity and T1 glottic cancers) need elective management of neck nodes – either by a neck dissection or neck irradiation. The level(s) of nodes to be treated depends on the primary site of tumour and T stage, and the choice of treatment modality depends on the treatment of the primary site (Box 8.3).

Box 8.3
Recommended elective node treatment in stage I–II (T1–2N0) head and neck cancer

Primary site Nodal irradiation in N0 disease Selective node dissection in N0 disease
Oral cavity:    
T2 well lateralized Ipsilateral level I–II I–III
T2 reaching midline Bilateral level I–III  
Oropharynx:    
T1 Tonsil Ipsilateral Ib–II II–IV
T2 lateralized tonsil Ipsilateral Ib–IV  
All other N0 Bilateral Ib–V  
Larynx:    
T1–2 Glottic No nodal radiotherapy II–IV and if extends below glottis, II–V
T1/2 Supraglottic Bilateral level Ib–III  
All other N0 Bilateral Ib–V  
Hypopharynx:    
All N0 Bilateral I–V II–V
Nasopharynx:    
T1N0 squamous carcinoma No neck irradiation –
All N0 Bilateral I–V  

Locally advanced disease (Stage III–IVb/T3–4N1–3M0)

Patients with locally advanced disease are treated with combined modality treatment. The treatment decision is based on chance of local control and outcome. The options are:

• Surgery followed by postoperative radiotherapy or chemoradiotherapy
• Radical chemoradiotherapy – option for organ preservation
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